Improving the Signal-In-Space Monitoring Accuracy of a Galileo External Regional Integrity System using Co-located Receiver Baselines

Aiden J.Deem, Yanming Feng

Abstract:	The Galileo GlobalNavigation Satellite System will provide the opportunity for regions to transmit regional integrity information for each Galileo satellite. This information is derived from an External Regional Integrity System (ERIS), which includes a network of regionally located Galileo Sensor Stations (GSSs). The literature to date has concentrated on defining the integrity concept for the globally available Galileo Safety-of-Life (SoL) service. This paper introduces concepts for deriving regional and local integrity as part of an ERIS. A regional network introduces a number of issues. For instance, the global network is able to continually monitor a given satellite, but a regional network must tolerate rising and setting satellites at the limits of the network coverage. The Service Region (SR) of the ERIS is geographically fixed — unlike the SoL service where the SR is the satellite footprint. In limiting the SR to high density and important user locations, remote locations are excluded from the ERIS network despite the fact that some GSSs are located in these areas. A local integrity service using a single station is desirable to service these remote areas. This can aslo be applied to GSSs near the boundary of the network SR to provide integrity for rising satellites not sufficiently monitored by the ERIS network. To allow satellites monitored by a single GSS to be integrated into the network users’ risk calculations, the single station concept must feature the same regional integrity parameters as the network concept. Furthermore, the Signal-In-SpaceMonitoring Accuracy (SISMA) / Integrity Flag (IF) method is used to maintain compliance with the Galileo Integrity Concept (GIC). This is significant because now integrity can be integrated at the global, regional and local scales. The single station concept is partially based on a LAAS Category III approach that uses short-baseline carrier-phase measurements for the monitoring of satellite ephemeris errors. Double-Difference (DD) carrier-phase measurements from multiple baselines are used in combination with a single pseudo-range measurement, and through the use of a least-squares estimator the three parameter Signal-In-Space Error (SISE) is calculated. A simulation study has been performed that shows expected values of the broadcast SISMA for satellites monitored by a single station. The local SISMA for satellites visible within 1–1000 km of the single station is assessed against the SoL service requirement for the SISMA of 0.7m. The results show a clear advantage for using the single station concept developed in this paper to provide integrity monitoring to local areas and also in situations where a regional ERIS does not have sufficient network geometry to meet the SoL SISMA requirement
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2565 - 2573
Cite this article:	J.Deem, Aiden, Feng, Yanming, "Improving the Signal-In-Space Monitoring Accuracy of a Galileo External Regional Integrity System using Co-located Receiver Baselines," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2565-2573.
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